Device for preparing butadiene

ABSTRACT

Provided is a device for preparing butadiene. The device includes an oxidative dehydrogenation reaction part, in which oxidative dehydrogenation of reaction raw materials containing butene, oxygen (O 2 ), steam, and a diluent gas is performed to obtain oxidative dehydrogenation reaction products containing butadiene; a cooling separation part for removing water from the reaction products; a condensation separation part for condensing hydrocarbons from the reaction products from which water is removed; an absorption separation part for recovering all hydrocarbons from the reaction products containing hydrocarbons not condensed in the condensation separation part; and a purification part for separating butadiene from crude hydrocarbons condensed in the condensation separation part, wherein n-butane remaining after butadiene is separated in the purification part is fed again into the oxidative dehydrogenation reaction part. The device can provide high-purity butadiene while reducing energy consumption and raw material and production costs, thereby improving economic efficiency of processes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending allowed U.S. patentapplication Ser. No. 16/073,279, filed Jul. 26, 2018, which is aNational Stage Application of International Application No.PCT/KR2017/014964, filed on Dec. 18, 2017, which claims priority toKorean Patent Application No. 10-2016-0182326, filed on Dec. 29, 2016 inthe Korean Intellectual Property Office, the disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method of preparing butadiene. Morespecifically, the present invention relates to a method of preparinghigh-purity butadiene, which is capable of improving economic efficiencyof processes by increasing productivity while reducing energyconsumption and raw material costs.

BACKGROUND ART

Butadiene, an important chemical, is used as an intermediary for variouspetrochemical products, and demand and value thereof are graduallyincreasing in the petrochemical market.

Butadiene can be extracted from the C4 fraction through naphtha crackingor obtained by direct dehydrogenation or oxidative dehydrogenation ofbutene.

There among, according to the method of preparing butadiene by oxidativedehydrogenation of butene, oxygen is used as a reactant, and twohydrogens are removed from butene to generate butadiene. In this case,water generated as a result of the reaction is stable. Thus, the methodis themodynamically very advantageous. In addition, since oxidativedehydrogenation is an exothermic reaction unlike direct dehydrogenation,butadiene may be obtained in a high yield even at low reactiontemperatures as compared with direct dehydrogenation. Therefore, usingthe method of preparing butadiene by oxidative dehydrogenation ofbutene, it is possible to effectively meet increasing demand forbutadiene.

In addition, according to the method of preparing butadiene by oxidativedehydrogenation of butene, in addition to raw materials, nitrogen,steam, or the like is added as a diluent gas for the purpose of reducingexplosion risk due to oxygen and for removal of heat of reaction. Whenhydrocarbons are isolated from reaction products including diluentgases, light gas species (COx, O₂, and the like), hydrocarbons, and thelike, a method of absorbing hydrocarbons from reaction products and amethod of liquefying hydrocarbons by cooling reaction products may beused. There among, the absorption method is mainly used. In the case ofthe liquefaction method, a very low-temperature refrigerant is requiredfor liquefaction due to diluent gases, light gas species, and the likepresent in reaction products. This increases equipment costs, operatingcosts, and energy consumption, which may lower economic efficiency ofprocesses. For this reason, the absorption method is preferred.

In this regard, a conventional device for preparing butadiene and aconventional method of preparing the same are described in FIG. 1.

Referring to FIG. 1, the conventional device includes an oxidativedehydrogenation reaction part 110 responsible for producing reactionproducts containing butadiene from reaction raw materials includingbutene, oxygen (O₂), steam, and a diluent gas (nitrogen); a coolingseparation part 120 responsible for removing water from the reactionproducts obtained by oxidative dehydrogenation; an absorption separationpart 130 responsible for separating butadiene or a C4 mixture containingbutadiene, and hydrocarbons from the oxidative dehydrogenation reactionproducts, from which water is removed; and a purification part 140responsible for purifying butadiene from the butadiene-containing streamseparated in the absorption separation part 130.

The oxidative dehydrogenation reaction part 110 may be operated to reactreaction raw materials including butene, oxygen (O₂), steam, a diluentgas (N₂), and unreacted butene recovered in the purification part in thepresence of a ferrite catalyst or a bismuth molybdate catalyst underisothermal or adiabatic conditions.

The cooling separation part 120 may be operated by a quenching-typedirect cooling system (quencher) or an indirect cooling system.

FIG. 1 shows an example of selectively absorbing and separating onlybutadiene in the absorption separation part 130. However, in theabsorption separation part 130, only butadiene may be selectivelyabsorbed from reaction products from which water is removed, or allhydrocarbons including a C4 mixture may be absorbed using a solvent.Specific examples of solvents capable of selectively absorbing butadienemay include acetonitrile (ACN), N-methylpyrrolidone (NMP), dimethylformamide (DMF), and the like, and specific examples of solvents capableof absorbing all hydrocarbons including a C4 mixture may includetoluene, xylene, and the like. In the absorption separation part 130,COx, O₂, and N₂ used as a diluent gas are all incinerated, or in somecases, a portion thereof is recovered in the reaction part and reused,and the remainder is incinerated.

For example, the purification part 140 is conventional butadienepurification equipment. In the purification part 140, an acetonitrile(ACN) process, a N-methylpyrrolidone (NMP) process, or a dimethylformamide (DMF) process may be performed. When necessary, parts of theseprocesses may be performed in modified form to purify butadiene.

However, in general, an excess of a solvent is used in an absorptionseparation process. Thus, a large amount of energy is consumed in theprocess of recovering an absorption solvent and the process ofrecovering and purifying butadiene in the purification part 140.Alternatively, when the absorption separation process is replaced by acondensation process, a very low-temperature refrigerant is required. Inthis case, energy consumption, raw material costs, and production costsare increased, thereby lowering economic efficiency of processes.Therefore, there is an urgent need to develop related technologies tosolve these problems.

PRIOR ART DOCUMENT

-   [Patent Document] (Patent Document 1) KR 10-2012-0103759 A

DISCLOSURE Technical Problem

Therefore, the present invention has been made in view of the aboveproblems, and it is one object of the present invention to provide amethod of preparing butadiene. According to the method of the presentinvention, when butadiene is prepared by oxidative dehydrogenation ofbutene, unlike conventional methods, in which nitrogen is used as adiluent gas and an absorption method is used to separate butadiene fromoxidative dehydrogenation reaction products, butane is used as a diluentgas and a condensation method, in which butadiene is liquefied andseparated from oxidative dehydrogenation reaction products using alow-temperature refrigerant or cooling water, is used. In particular, tominimize loss of active ingredients (all hydrocarbons includingbutadiene) discharged with a stream including COx, O₂, n-butane, and thelike separated in a condensation process, a method of recovering allactive ingredients from an upper stream generated in the condensationprocess is used.

The above and other objects can be accomplished by the presentdisclosure described below.

Technical Solution

In accordance with one aspect of the present invention, provided is amethod of preparing butadiene, including

a step of obtaining oxidative dehydrogenation reaction productscontaining butadiene, which are generated when reaction raw materialscontaining butene, oxygen (O₂), steam, and a diluent gas are passedthrough an oxidative dehydrogenation reaction part;

a step of removing water from the oxidative dehydrogenation reactionproducts containing butadiene by passing the oxidative dehydrogenationreaction products through a cooling separation part;

a step of condensing hydrocarbons by passing the oxidativedehydrogenation reaction products, from which water is removed, througha condensation separation part;

a step of recovering all hydrocarbons not condensed in the condensationseparation part by passing oxidative dehydrogenation reaction productscontaining hydrocarbons not condensed in the condensation separationpart through an absorption separation part; and

a step of separating butadiene by passing crude hydrocarbons includingn-butane, butene, butadiene, and the like, which are condensed in thecondensation separation part, and crude hydrocarbons including n-butane,butene, butadiene, and the like, which are recovered in the absorptionseparation part, through a purification part,

wherein n-butane and butene excluding butadiene, which are separated inthe purification part, are fed again into the oxidative dehydrogenationreaction part, and the diluent gas is butane.

In accordance with another aspect of the present invention, provided isa device for preparing butadiene, including an oxidative dehydrogenationreaction part, in which oxidative dehydrogenation of reaction rawmaterials containing butene, oxygen (O₂), steam, and a diluent gas isperformed to obtain oxidative dehydrogenation reaction productscontaining butadiene;

a cooling separation part responsible for removing water from theoxidative dehydrogenation reaction products resulting from oxidativedehydrogenation;

a condensation separation part responsible for condensing hydrocarbonsfrom the oxidative dehydrogenation reaction products, from which wateris removed;

an absorption separation part responsible for recovering allhydrocarbons from oxidative dehydrogenation reaction products containinghydrocarbons not condensed in the condensation separation part; and

a purification part responsible for separating butadiene from crudehydrocarbons including n-butane, butene, butadiene, and the like, whichare condensed in the condensation separation part, and crudehydrocarbons including n-butane, butene, butadiene, and the like, whichare recovered in the absorption separation part, wherein n-butane andbutene excluding butadiene, which are separated in the purificationpart, are fed again into the oxidative dehydrogenation reaction part,and the diluent gas is butane.

Advantageous Effects

As apparent from the foregoing, the present invention advantageouslyprovides a method of preparing butadiene. According to the presentinvention, when butadiene is prepared by oxidative dehydrogenation ofbutene, unlike conventional methods, in which nitrogen is used as adiluent gas and an absorption method is used to separate butadiene fromoxidative dehydrogenation reaction products, butane is used as a diluentgas and a condensation method, in which butadiene is liquefied andseparated from oxidative dehydrogenation reaction products using alow-temperature refrigerant or cooling water, is used. In addition, anabsorption method of recovering all hydrocarbons from an upper streamgenerated in a condensation process is used, so that loss ofhydrocarbons is minimized. Therefore, the method of the presentinvention can reduce energy consumption, raw material costs, andproduction costs, thereby improving economic efficiency of processes.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram for explaining a conventional device forpreparing butadiene and a conventional method of preparing the same.

FIGS. 2 to 6 are schematic diagrams for explaining the device forpreparing butadiene and the method of preparing the same according tothe present invention.

BEST MODE

Hereinafter, the method of preparing butadiene and the device forpreparing the same according to the present invention will be describedin detail. According to the present invention, butane is used as adiluent gas when a condensation separation process is performed, and anabsorption separation process, in which all active ingredients containedin a stream discharged to the outside through the upper portion of acondensation separation part are recovered, is employed. In the casethat butane is used as a diluent gas as described above, in thecondensation separation process, hydrocarbons may be easily separatedfrom oxidative dehydrogenation reaction products using a low-temperaturerefrigerant or cooling water, and in an absorption separation part, allhydrocarbons discharged to the outside are recovered to minimize loss ofactive ingredients discharged to the outside of the system. Thus, whenthe method and device of the present invention are used, high-puritybutadiene may be prepared while reducing production costs.

The method of preparing butadiene and the device for preparing the sameaccording to the present invention will be described in detail withreference to the accompanying drawings. FIGS. 2 to 6 are schematicdiagrams for explaining the device for preparing butadiene and themethod of preparing the same according to the present invention.

Referring to FIG. 2, first, reaction raw materials containing butene,oxygen (O₂), steam, and a diluent gas (butane) are passed through anoxidative dehydrogenation reaction part 210 to obtain oxidativedehydrogenation reaction products containing butadiene. In this case,raw materials used for oxidative dehydrogenation may be combined withdischarge streams B7 and B8 resulting from a purification process andintroduced into the oxidative dehydrogenation reaction part 210, and astream B1 resulting from the reaction process may include butadiene,n-butane, butene, O₂, COx, H₂O, and the like. The discharge stream B1generated in the oxidative dehydrogenation reaction part 210 isintroduced into a cooling separation part 220 and water is separatedtherein.

A discharge stream B2 generated after the cooling separation process maycontain butadiene, n-butane, butene, O₂, COx, and the like, and thedischarge stream B2 is introduced into a condensation separation part230.

A discharge stream B3 generated after the condensation separationprocess may contain oxidative dehydrogenation reaction productscontaining hydrocarbons, which are not condensed after condensation ofhydrocarbons is performed using cooling water, and the like according toa compression/cooling manner in the condensation separation part. Thedischarge stream B3 may be introduced into an absorption separation part250, and hydrocarbons may be recovered.

Another discharge stream B4 generated after the condensation separationprocess may contain crude hydrocarbons including n-butane, butene, andbutadiene, which are condensed in the condensation separation part 230.The discharge stream B4 may be introduced into a purification part 240,and butadiene may be purified.

A discharge stream B5 generated after the absorption separation processmay contain O₂, COx, and the like, which are separated in the previouscondensation separation process, and another discharge stream B6generated after the absorption separation process may contain crudehydrocarbons including n-butane, butene, butadiene, and the likeexcluding COx and O₂, which are separated in the absorption separationpart 250. Butadiene may be separated by passing the discharge streams B6through the purification part 240.

A discharge stream B7 generated after the purification process maycontain a large amount of residual n-butane, and a recirculation stream,in which the stream B7 is fed again into the oxidative dehydrogenationreaction part 210, may be formed. A discharge stream B8 containingbutene remaining after butadiene is separated in the purification part240 may be fed again into the oxidative dehydrogenation reaction part210, thereby forming a recirculation stream.

The term “crude hydrocarbons” refers to crude hydrocarbons commonly usedin the art to which the present invention pertains. Unless otherwisespecified herein, the crude hydrocarbons refer to hydrocarbons includingbutadiene and the like recovered from oxidative dehydrogenation reactionproducts, and are used as raw materials in the purification part.

The term “COx” refers to CO and CO₂ unless otherwise specified herein.

In the present invention, butene may be 1-butene, 2-butene, or a mixturethereof. Raw materials containing butene generally used to preparebutadiene are not particularly limited and may be used as the rawmaterials containing butene of the present invention.

For example, butene may be obtained from a hydrocarbon mixture includingbutenes, such as raffinate-2 and raffinate-3, included in the C4fraction produced when high-purity butene and naphtha are decomposed.

The steam is a gas which is injected for the purpose of preventingcoking of a catalyst and removing heat of reaction while reducing riskof explosion of reactants when oxidative dehydrogenation is performed.

In the present invention, oxygen (O₂) reacts with butene as an oxidizingagent to cause dehydrogenation.

Any catalysts may be used as the catalyst of the present inventionpacked in the reactor without any particular limitation as long as thecatalysts are capable of catalyzing oxidative dehydrogenation of buteneto prepare butadiene. For example, ferrite catalysts or bismuthmolybdate catalysts may be included.

In one embodiment of the present invention, the catalyst may be aferrite catalyst. In particular, when zinc ferrite, magnesium ferrite,or manganese ferrite is used, selectivity for butadiene may beincreased. The kind and amount of the reaction catalyst may varydepending on specific reaction conditions.

The diluent gas may be butane.

For example, the oxidative dehydrogenation reaction part 210 may beoperated under isothermal or adiabatic conditions, in which case freshlysupplied butene, oxygen (O₂), steam, re-supplied n-butane and butene areused as reaction raw materials, and a ferrite catalyst is used as acatalyst, wherein re-supplied n-butane and butene are residues remainingafter butadiene is separated in the purification part 240 and are fedagain into the oxidative dehydrogenation reaction part.

For example, oxygen (O₂) contained in the reaction raw materials may befed in a gaseous form having a purity of 90% or more, 95% or more, or95% or more.

Feeding of oxygen (O₂) in a gaseous form having a purity of 90% or morerefers that oxygen is not supplied from air, but is fed in a pure oxygenform. Thus, by measuring the amount of active ingredients in real time,it is possible to control the amount of each of components contained inreaction raw materials fed into a reactor.

For example, in the oxidative dehydrogenation reaction part 210,oxidative dehydrogenation may be performed in a molar ratio ofbutene:oxygen:steam:diluent gas (n-butane)=1:0.5 to 3:0.1 to 20:0.1 to20. Within this range, energy consumption and raw material costs may bereduced, and productivity may be improved, thereby increasing economicefficiency of processes.

As a particular example, the oxidative dehydrogenation reaction part 210is preferably operated in a molar ratio of oxygen:butene=0.5 to 3:1, amolar ratio of steam:butene=1 to 20:1, and a molar ratio ofn-butane:butene=0.1 to 20:1 at a reaction pressure of atmosphericpressure to 10 atm and a reaction temperature of 150 to 650° C. underisothermal or adiabatic conditions. Within this range, energyconsumption and raw material costs may be reduced, and productivity maybe improved, thereby increasing economic efficiency of processes.

For example, the cooling separation part 220 may be operated by aquenching-type direct cooling system (quencher) or an indirect coolingsystem. In this case, the cooling separation part may be rapidly cooledto a temperature of 0 to 100° C.

For example, the condensation separation part 230 may have asingle-stage compression structure having one stage or a multistagecompression structure having 1 to 10 stages or 1 to 2 stages. Whencompressing from an initial pressure to a target pressure at a time, alot of power is required. In addition, heat is generated due to gascompression, which causes gas expansion, resulting in poor compressionefficiency. Therefore, to prevent such problems, multi-stage compressionis performed. In this case, heat generated in the compression processmay be cooled using a cooler.

In the condensation separation part 230, condensation conditions may bedetermined so that the stream of the condensation separation part 230 isout of an explosive range in consideration of unreacted oxygen (i.e.,above upper explosive limit or below limiting oxygen concentration).

In one embodiment of the present invention, a refrigerant used in thecondensation separation part 230 may be one or more selected from thegroup consisting of cooling water, ethylene glycol, an aqueous solutionof ethylene glycol having a concentration of 20 to 100% by weight,propylene glycol, an aqueous solution of propylene glycol having aconcentration of 30 to 100% by weigh, and a propylene-based solvent.

For example, the propylene-based solvent, as a compound includingpropylene or propylene, may have a boiling point of −10° C. or less or−10 to −50° C.

As a particular example, the refrigerant may be cooling water, coolingwater having a temperature of 0 to 40° C., or cooling water having atemperature of 5 to 30° C. In this case, the extrusion dischargetemperature may be 250° C. or less or 50 to 250° C., and the coolingtemperature of a compression discharge stream may be 120° C. or less or20 to 80° C.

Conventionally, since nitrogen is used as a diluent gas, a verylow-temperature refrigerant is required when a dilution gas and lightgas species are separated using a condensation method. In the presentinvention, since butane is used as a diluent gas, a lower grade ofrefrigerant may be used.

For example, a conventional apparatus for purifying butadiene may beused as the purification part 240. For example, in the purification part240, an acetonitrile (ACN) process, a N-methylpyrrolidone (NMP) process,or a dimethyl formamide (DMF) process may be performed.

For example, the absorption separation part 250 may be operated in anabsorption manner, in which toluene, xylene, or the like is used as asolvent for absorbing all hydrocarbons.

In a purification step, solvents, high boiling point components and lowboiling point components are removed from reaction products containingbutadiene obtained in the separation step, and thus high-puritybutadiene may be obtained.

In one embodiment of the present invention, the purity of finallyobtained butadiene through the series of steps described above may be95.0 to 99.9%.

FIG. 3 is a schematic diagram showing a process, in which oxidativedehydrogenation reaction products, from which water is removed in thecooling separation part 220 as shown in FIG. 2, are fed into apurification part 240 (via streams B4 and B6) through the condensationseparation part 230 and the absorption separation part 250. At thistime, the process is explained including a degasification part and asolvent recovery part.

For example, the degasification part and the solvent recovery part maybe operated by stripping using a conventional column, or degasification.

Referring to FIG. 3, first, oxidative dehydrogenation reaction productscontaining butadiene are obtained by passing reaction raw materialscontaining butene, oxygen (O₂), steam, and a diluent gas (butane)through an oxidative dehydrogenation reaction part 310. At this time,raw materials for oxidative dehydrogenation may be combined with thedischarge streams B7 and B8 generated after the purification process,and introduced into the oxidative dehydrogenation reaction part 310. Thestream B1 resulting from the reaction process may include butadiene,n-butane, butene, O₂, COx, H₂O, and the like.

The stream B1 discharged from the oxidative dehydrogenation reactionpart 310 is introduced into a cooling separation part 320, and water isremoved from the stream B1.

The discharge stream B2 generated after the cooling separation processmay contain butadiene, n-butane, butene, O₂, COx, and the like. Thedischarge stream B2 is introduced into the condensation separation part,and hydrocarbons are condensed.

The discharge stream B3 generated after the condensation separationprocess may contain oxidative dehydrogenation reaction productscontaining hydrocarbons not condensed when hydrocarbons are condensedusing cooling water through compression/cooling in the condensationseparation process. The discharge stream B3 is introduced into anabsorption separation part 350.

The discharge stream B5 generated after the absorption separationprocess may contain O₂, COx, and the like, which are separated in theprevious condensation separation process. A discharge stream B6′generated after the absorption separation process may contain a solvent,in which hydrocarbons including n-butane, butene, butadiene, and thelike excluding COx and O₂, which are generated in the absorptionseparation part 350, are absorbed. The discharge stream B6′ may beintroduced into a solvent recovery part 370 to recover the solvent, andthe recovered solvent may be fed again into the absorption separationpart 350 through a discharge stream B9.

Another discharge stream B10 generated after the solvent is recoveredand a discharge stream B4′ containing hydrocarbons condensed in acondensation separation part 330 may be introduced into a degasificationpart 360 to additionally separate COx and O₂.

A discharge stream B11 generated after the degasification process maycontain COx and O₂ additionally separated in the degasification part360, and may be introduced into the absorption separation part 350 andan absorption separation process may be performed. Another dischargestream B4″ generated after the degasification process may contain crudehydrocarbons including n-butane, butene, and butadiene excluding COx andO₂, which are additionally separated in the degasification part 360, andmay be introduced into a purification part 340 to separate butadiene.

The discharge stream B7 generated after the purification process maycontain a large amount of residual n-butane, and a recirculation stream,in which the discharge stream B7 is introduced into the oxidativedehydrogenation reaction part 310, may be formed.

The discharge stream B8 containing butene remaining after butadiene isseparated in the purification part 340 may be mixed with butene suppliedas a raw material, and form a recirculation stream, in which the streamis introduced into the oxidative dehydrogenation reaction part 310.

FIG. 4 is a schematic diagram showing a process, in which anotherdischarge stream B4′″ is additionally added to the discharge stream B4″generated after the degasification process in FIG. 3. The dischargestream B4″ may contain crude hydrocarbons including n-butane, butene,butadiene, high-boiling point materials, and the like excluding COx andO₂, which are additionally separated in a degasification part 460. Thedischarge stream B4′″, in which high-boiling point materials areseparated in a high-boiling point material removal part 480, may includecrude hydrocarbons including n-butane, butene, butadiene, and the like,from which high-boiling point materials are removed, and may be purifiedin a purification part 440.

For example, the high-boiling point material removal part 480 may beoperated according to a distillation method.

For example, the high-boiling point materials may be aromatichydrocarbons, such as benzene, styrene, and phenol, butadiene dimers,acetophenone, benzophenone, or anthraquinone.

Referring to FIG. 4, first, reaction raw materials containing butene,oxygen (O₂), steam, and a diluent gas (butane) are passed through anoxidative dehydrogenation reaction part 410 to obtain oxidativedehydrogenation reaction products containing butadiene. At this time,raw materials for oxidative dehydrogenation may be combined with thedischarge streams B7 and B8 generated after the purification process,and introduced into the oxidative dehydrogenation reaction part 410. Thestream B1 discharged after the process may contain butadiene, n-butane,butene, O₂, COx, H₂O, and the like. The stream B1 discharged from theoxidative dehydrogenation reaction part 410 is introduced into a coolingseparation part 420, and water is removed.

As in FIG. 3, the discharge stream B2 generated after the coolingseparation process may contain butadiene, n-butane, butene, O₂, COx, andthe like, and may be introduced into a condensation separation part 430.

The discharge stream B3 generated after the condensation separationprocess may contain oxidative dehydrogenation reaction productscontaining hydrocarbons not condensed when hydrocarbons are condensedusing cooling water through compression/cooling in the condensationseparation process, and may be introduced into an absorption separationpart 450.

The discharge stream B5 generated after the absorption separationprocess may contain O₂, COx, and the like, which are separated in theprevious condensation separation process. The discharge stream B6′generated after the absorption separation process may contain a solvent,in which hydrocarbons including n-butane, butene, butadiene, and thelike excluding COx and O₂ are absorbed in the absorption separation part450. The discharge stream B6′ may be passed through a solvent recoverypart 470 to recover the solvent, and the recovered solvent may be fedagain into the absorption separation part 450 through the dischargestream B9.

Another discharge stream B10 generated after the solvent is recoveredand the discharge stream B4′ containing hydrocarbons condensed in thecondensation separation part 430 may be passed through thedegasification part 460 to additionally separate COx and O₂.

The discharge stream B11 generated after the degasification process maycontain COx and O₂ additionally separated in the degasification part460. The discharge stream B11 may be fed into the absorption separationpart 450, and absorption separation may be performed. Another dischargestream B4″ generated after the degasification process may contain crudehydrocarbons including n-butane, butene, and butadiene, high-boilingpoint materials, and the like excluding COx and O₂, which areadditionally separated in the degasification part 460, and may beintroduced into the high-boiling point material removal part 480, andhigh-boiling point materials are removed.

For example, the high-boiling point materials may be aromatichydrocarbons, such as benzene, styrene, and phenol, butadiene dimers,acetophenone, benzophenone, or anthraquinone.

The discharge stream B4′″ generated after the high-boiling pointmaterials are removed may contain crude hydrocarbons including n-butane,butene, butadiene, and the like, from which high-boiling point materialsare removed, and may be fed into the purification part 440 to separatebutadiene.

The discharge stream B7 generated after the purification process maycontain a large amount of residual n-butane. A recirculation stream, inwhich the discharge stream B7 is introduced into the oxidativedehydrogenation reaction part 410, may be formed.

The discharge stream B8 containing residual butene remaining afterbutadiene is separated in the purification part 440 may be combined withbutene supplied as a raw material and fed into the oxidativedehydrogenation reaction part 410, resulting in formation of arecirculation stream.

FIG. 5 is a schematic diagram showing a case where the discharge streamB11 generated after the degasification process in FIG. 3 is replacedwith another discharge stream B11′. In this case, gas separationefficiency may be improved by feeding COx and O₂ separated in adegasification part 560 into the condensation system.

Unless otherwise specified herein, the condensation system refers to asystem including a compressor 531, a heat exchanger 532, and acondensation separation part 530.

Referring to FIG. 5, first, reaction raw materials containing butene,oxygen (O₂), steam, and a diluent gas (butane) are passed through anoxidative dehydrogenation reaction part 510 to obtain oxidativedehydrogenation reaction products containing butadiene. At this time,raw materials for oxidative dehydrogenation may be combined with thedischarge streams B7 and B8 generated after the purification process,and introduced into the oxidative dehydrogenation reaction part 510. Thestream B1 discharged after the process may contain butadiene, n-butane,butene, O₂, COx, H₂O, and the like. The stream B1 discharged from thereaction part is introduced into a cooling separation part 520, andwater is removed.

The discharge stream B2 generated after the cooling separation processmay contain butadiene, n-butane, butene, O₂, COx, and the like, and maybe introduced into the condensation separation part.

The discharge stream B3 generated after the condensation separationprocess may contain oxidative dehydrogenation reaction productscontaining hydrocarbons not condensed when hydrocarbons are condensedusing cooling water through compression/cooling in the condensationseparation process. The discharge stream B3 may be introduced into anabsorption separation part 550.

The discharge stream B5 generated after the absorption separationprocess may contain O₂, COx, and the like, which are separated in theprevious condensation separation process. Another discharge stream B6′generated after the absorption separation process may contain a solvent,in which hydrocarbons including n-butane, butene, butadiene, and thelike excluding COx and O₂ are absorbed in the absorption separation part550. The discharge stream B6′ may be passed through a solvent recoverypart 570 to recover the solvent, and the recovered solvent may be fedagain into the absorption separation part 550 through the dischargestream B9.

Another discharge stream B10 generated after the solvent is recovered,and the discharge stream B4′ containing hydrocarbons condensed in thecondensation separation part may be passed through the degasificationpart 560 to additionally separate COx and O₂.

The discharge stream B11′ generated after the degasification process maycontain COx and O₂ additionally separated in the degasification part560. The discharge stream B11′ may be introduced into the condensationsystem, and condensation separation may be performed in the condensationseparation part 530. Another discharge stream B4″ generated after thedegasification process may contain crude hydrocarbons includingn-butane, butene, butadiene, and the like excluding COx and O₂, whichare additionally separated in the degasification part 560. The dischargestream B4″ may be fed into a purification part 540 to separatebutadiene.

Unless otherwise specified herein, the condensation system refers to asystem including the compressor 531 the heat exchanger 532 and thecondensation separation part 530.

The discharge stream B7 generated after the purification process maycontain a gas containing a large amount of residual n-butane, and form arecirculation stream, in which the discharge stream B7 is introducedinto the oxidative dehydrogenation reaction part 510. The dischargestream B8 containing residual butene remaining after butadiene isseparated in the purification part 540 may be combined with butenesupplied as a raw material, and introduced into the oxidativedehydrogenation reaction part 510, resulting in formation of arecirculation stream.

FIG. 6 is a schematic diagram showing a case where the discharge streamB11 generated after the degasification process in FIG. 4 is replacedwith another discharge stream B11′. In this case, when COx and O₂separated in a degasification part 660 are fed into the condensationsystem, COx and O₂ are circulated to a condensation separation part 630,thereby improving gas separation efficiency.

Referring to FIG. 6, first, reaction raw materials containing butene,oxygen (O₂), steam, and a diluent gas (butane) are passed through anoxidative dehydrogenation reaction part 610 to obtain oxidativedehydrogenation reaction products containing butadiene. At this time,raw materials for oxidative dehydrogenation may be combined with thedischarge streams B7 and B8 generated after the purification process,and introduced into the oxidative dehydrogenation reaction part 610. Thestream B1 discharged after the process may contain butadiene, n-butane,butene, O₂, COx, H₂O, and the like. The discharge stream B1 generatedafter the reaction process is introduced into a cooling separation part620.

As in FIG. 5, the discharge stream B2 generated after the coolingseparation process may contain butadiene, n-butane, butene, O₂, COx, andthe like, and introduced into the condensation separation part.

The discharge stream B3 generated after the condensation separationprocess may contain oxidative dehydrogenation reaction productscontaining hydrocarbons not condensed when hydrocarbons are condensedusing cooling water through compression/cooling in the condensationseparation process. The discharge stream B3 is introduced into anabsorption separation part 650.

The discharge stream B5 generated after the absorption separationprocess may contain O₂, COx, and the like, which are not separated inthe previous condensation separation process. Another discharge streamB6′ generated after the absorption separation process may contain asolvent, in which hydrocarbons including n-butane, butene, butadiene,and the like excluding COx and O₂, which are separated in the absorptionseparation part 650, are absorbed. The discharge stream B6′ may bepassed through a solvent recovery part 670 to recover the solvent, andthe recovered solvent may be fed again into the absorption separationpart 650 through the discharge stream B9.

Another discharge stream B10 generated after the solvent is recovered,and the discharge stream B4′ containing hydrocarbons condensed in thecondensation separation part 630 may be passed through thedegasification part 660 to additionally separate COx and O₂.

The discharge stream B11′ generated after the degasification process maycontain COx and O₂ additionally separated in the degasification part660. The discharge stream B11′ may be fed into the condensation system,and recondensation may be performed therein.

Unless otherwise specified herein, the condensation system refers to asystem including a compressor 631, a heat exchanger 632, and thecondensation separation part 630.

Another discharge stream B4″ generated after the degasification processmay contain crude hydrocarbons including butane, butene, butadiene,high-boiling point materials, and the like excluding COx and O₂, whichare additionally separated in the degasification part 660. The dischargestream B4″ is introduced into a high-boiling point material removal part680, and high-boiling point materials are separated. The dischargestream B4′″ generated in the high boiling point removal process maycontain crude hydrocarbons including n-butane, butene, butadiene, andthe like, from which high-boiling point materials are removed, and fedinto a purification part 640 to separate butadiene.

The discharge stream B7 generated after the purification process maycontain a large amount of residual n-butane, and form a recirculationstream, in which the discharge stream B7 is fed into the oxidativedehydrogenation reaction part 610. The discharge stream B8 containingresidual butene remaining after butadiene is separated in thepurification part 640 may form a recirculation stream, in which thedischarge stream B8 is fed into the oxidative dehydrogenation reactionpart 610.

For example, a device used in the method of the present invention,referring to FIG. 2, includes the oxidative dehydrogenation reactionpart 210, in which oxidative dehydrogenation of reaction raw materialscontaining butene, oxygen (O₂), steam, and a diluent gas (butane) isperformed to obtain oxidative dehydrogenation reaction productscontaining butadiene; a cooling separation part 220 responsible forremoving water from the oxidative dehydrogenation reaction productscontaining butadiene; the condensation separation part 230 responsiblefor condensing hydrocarbons from the oxidative dehydrogenation reactionproducts, from which water is removed; the absorption separation part250 responsible for recovering all hydrocarbons from oxidativedehydrogenation reaction products containing hydrocarbons not condensedin the condensation separation part 230; and the purification part 240responsible for separating butadiene from a discharge stream containingcrude hydrocarbons including n-butane, butene, butadiene, and the like,which are condensed in the condensation separation part 230, wherein thedevice is configured so that the discharge stream B7 containing n-butaneexcluding butadiene separated in the purification part 240 is fed againinto the oxidative dehydrogenation reaction part 210.

The device is configured so that the discharge stream B6 containingcrude hydrocarbons including n-butane, butene, butadiene, and the like,which are recovered in the absorption separation part 250, is fed intothe purification part 240.

The device is configured so that the discharge stream B8 containingbutene remaining after butadiene is separated in the purification part240 is fed again into the oxidative dehydrogenation reaction part 210.

As another example, a device for preparing butadiene, referring to FIG.3, includes the oxidative dehydrogenation reaction part 310, in whichoxidative dehydrogenation of reaction raw materials containing butene,oxygen (O₂), steam, and a diluent gas (butane) is performed to obtainoxidative dehydrogenation reaction products containing butadiene; acooling separation part 320 responsible for removing water from theoxidative dehydrogenation reaction products containing butadiene; thecondensation separation part 330 responsible for condensing hydrocarbonsfrom the oxidative dehydrogenation reaction products, from which wateris removed; and the absorption separation part 350 responsible forrecovering all hydrocarbons from oxidative dehydrogenation reactionproducts containing hydrocarbons not condensed in the condensationseparation part 330.

The device is configured so that the discharge stream B6′ containinghydrocarbons including n-butane, butene, butadiene, and the like, whichare recovered in the absorption separation part 350, is fed into thesolvent recovery part 370 responsible for recovering a solvent, and thedischarge stream B9 containing the solvent recovered in the solventrecovery part 370 is recycled to the absorption separation part 350.

Preferably, the device further includes the degasification part 360responsible for separating COx, O₂, hydrocarbons including n-butane,butene, butadiene, and the like from the discharge stream B4′ consistingof hydrocarbons including n-butane, butene, butadiene, and the like,which are condensed in the condensation separation part 330, and thedischarge stream B10 consisting of hydrocarbons including n-butane,butene, butadiene, and the like, from which the solvent is removed inthe solvent recovery part 370.

The device is configured so that the discharge stream B11 containing COxand O₂ separated in the degasification part 360 is introduced into theabsorption separation part 350.

The device is configured so that the discharge stream B4″ containingcrude hydrocarbons including n-butane, butene, butadiene, and the likeexcluding COx and O₂, which are separated in the degasification part360, is fed into the purification part 340.

The device further includes the purification part 340 for separatingbutadiene, and is configured so that the discharge stream B7 containingn-butane excluding butadiene separated in the purification part 340 isfed again into the oxidative dehydrogenation reaction part 310. Inaddition, the device is configured so that the discharge stream B8containing butene remaining after butadiene is separated in thepurification part 340 is combined with butene supplied as a raw materialand fed again into the oxidative dehydrogenation reaction part 310.

As another example, a device for preparing butadiene, referring to FIG.4, includes the oxidative dehydrogenation reaction part 410, in whichoxidative dehydrogenation of reaction raw materials containing butene,oxygen (O₂), steam, and a diluent gas (butane) is performed to obtainoxidative dehydrogenation reaction products containing butadiene; acooling separation part 420 responsible for removing water from theoxidative dehydrogenation reaction products containing butadiene; thecondensation separation part 430 responsible for condensing hydrocarbonsfrom the oxidative dehydrogenation reaction products, from which wateris removed; and the absorption separation part 450 responsible forrecovering all hydrocarbons from oxidative dehydrogenation reactionproducts containing hydrocarbons not condensed in the condensationseparation part 430.

The device is configured so that the discharge stream B6′ containinghydrocarbons including n-butane, butene, butadiene, and the like, whichare recovered in the absorption separation part 450, is fed into thesolvent recovery part 470 responsible for recovering the solvent, andthe discharge stream B9 containing the solvent recovered in the solventrecovery part 470 is recycled to the absorption separation part 450.

Preferably, the device further includes the degasification part 460responsible for separating COx, O₂, hydrocarbons including n-butane,butene, butadiene, and the like from the discharge stream B4′ consistingof hydrocarbons including n-butane, butene, butadiene, and the like,which are condensed in a condensation separation part 420, and thedischarge stream B10 consisting of hydrocarbons including n-butane,butene, butadiene, and the like, from which the solvent is removed inthe solvent recovery part 470.

The device is configured so that the discharge stream B11 containing COxand O₂ separated in the degasification part 460 is introduced into theabsorption separation part 450.

The device is configured so that the discharge stream B4″ containingcrude hydrocarbons including n-butane, butene, butadiene, high-boilingpoint materials, and the like excluding COx and O₂, which are separatedin the degasification part 460, is fed into the high-boiling pointmaterial removal part 480 to remove high-boiling point materials, andthe discharge stream B4′″ containing crude hydrocarbons includingn-butane, butene, butadiene, and the like, which are separated in thehigh-boiling point material removal part 480, is fed into thepurification part 440.

The device further includes the purification part 440 responsible forseparating butadiene, and is configured so that the discharge stream B7containing n-butane excluding butadiene separated in the purificationpart 440 is fed again into the oxidative dehydrogenation reaction part410.

The device is configured so that the discharge stream B8 containingresidual butene remaining after butadiene is separated in thepurification part 440 is fed again into the oxidative dehydrogenationreaction part 410.

As another example, a device for preparing butadiene, referring to FIG.5, includes the oxidative dehydrogenation reaction part 510, in whichoxidative dehydrogenation of reaction raw materials containing butene,oxygen (O₂), steam, and a diluent gas (butane) is performed to obtainoxidative dehydrogenation reaction products containing butadiene; acooling separation part 520 responsible for removing water from theoxidative dehydrogenation reaction products containing butadiene; thecondensation separation part 530 responsible for condensing hydrocarbonsfrom the oxidative dehydrogenation reaction products, from which wateris removed; and the absorption separation part 550 responsible forrecovering all hydrocarbons not condensed in the condensation separationpart 530.

The device is configured so that the discharge stream B6′ containinghydrocarbons including n-butane, butene, butadiene, and the like, whichare recovered in the absorption separation part 550, is fed into thesolvent recovery part 570 responsible for recovering the solvent, andthe discharge stream B9 containing the solvent recovered in the solventrecovery part 570 is recycled to the absorption separation part 550.

Preferably, the device further includes the degasification part 560responsible for separating COx, O₂, and hydrocarbons including n-butane,butene, butadiene, and the like from the discharge stream B4′ consistingof hydrocarbons including n-butane, butene, butadiene, and the like,which are condensed in the condensation separation part 530, and thedischarge stream B10 consisting of hydrocarbons including n-butane,butene, butadiene, and the like, from which the solvent is removed inthe solvent recovery part 570.

The device is configured so that the discharge stream B4″ containingcrude hydrocarbons including n-butane, butene, butadiene, and the likeexcluding COx and O₂, which are separated in the degasification part560, is fed into the purification part 540, and another discharge streamB11′ containing COx and O₂ separated in the degasification part 560 isfed into the condensation system.

Unless otherwise specified herein, the condensation system refers to asystem including the compressor 531, the heat exchanger 532, and thecondensation separation part 530.

The device further includes the purification part 540 responsible forseparating butadiene, and is configured so that the discharge stream B7containing n-butane excluding butadiene separated in the purificationpart 540 is fed again into the oxidative dehydrogenation reaction part510. In addition, the device is configured so that the discharge streamB8 containing residual butene remaining after butadiene is separated inthe purification part 540 is combined with butene supplied as a rawmaterial, and fed again into the oxidative dehydrogenation reaction part510.

As another example, a device for preparing butadiene, referring to FIG.6, includes the oxidative dehydrogenation reaction part 610, in whichoxidative dehydrogenation of reaction raw materials containing butene,oxygen (O₂), steam, and a diluent gas (butane) is performed to obtainoxidative dehydrogenation reaction products containing butadiene; acooling separation part 620 responsible for removing water from theoxidative dehydrogenation reaction products containing butadiene; thecondensation separation part 630 responsible for condensing hydrocarbonsfrom the oxidative dehydrogenation reaction products, from which wateris removed; and the absorption separation part 650 responsible forrecovering all hydrocarbons from oxidative dehydrogenation reactionproducts containing hydrocarbons not condensed in the condensationseparation part 630.

The device is configured so that the discharge stream B6′ containinghydrocarbons including n-butane, butene, butadiene, and the like, whichare recovered in the absorption separation part 650, is fed into thesolvent recovery part 670 responsible for recovering the solvent, andthe discharge stream B9 containing the solvent recovered in the solventrecovery part 670 is recycled to the absorption separation part 650.

Preferably, the device further includes the degasification part 660responsible for separating COx, O₂, and hydrocarbons including n-butane,butene, butadiene, and the like from the discharge stream B4′ consistingof hydrocarbons including n-butane, butene, butadiene, and the like,which are condensed in the condensation separation part 630, and thedischarge stream B10 consisting of hydrocarbons including n-butane,butene, butadiene, and the like, from which the solvent is removed inthe solvent recovery part 670.

The device is configured so that the discharge stream B11′ containingCOx and O₂ separated in the degasification part 660 is fed into thecondensation system.

Unless otherwise specified herein, the condensation system refers to asystem including the compressor 631, the heat exchanger 632, and thecondensation separation part 630.

The device is configured so that the discharge stream B4″ containingcrude hydrocarbons including n-butane, butene, butadiene, high-boilingpoint materials, and the like excluding COx and O₂, which are separatedin the degasification part 660, is fed into the high-boiling pointmaterial removal part 680 to remove high-boiling point materials, andthe discharge stream B4′″ containing crude hydrocarbons includingn-butane, butene, butadiene, and the like, which are separated in thehigh-boiling point material removal part 680, is fed into thepurification part 640.

The device further includes the purification part 640 responsible forseparating butadiene, and is configured so that the discharge stream B7containing n-butane excluding butadiene separated in the purificationpart 640 is fed again into the oxidative dehydrogenation reaction part610. In addition, the device is configured so that the discharge streamB8 containing residual butene remaining after butadiene is separated inthe purification part 640 is combined with butene supplied as a rawmaterial and fed again into the oxidative dehydrogenation reaction part610.

In summary, when the method of preparing butadiene and the device forpreparing the same according to the present invention are used, aconvention method of preparing butadiene by oxidative dehydrogenation ofbutene may be used, and butadiene may be separated from reactionproducts resulting from oxidative dehydrogenation by a liquefactionprocess using a low-temperature refrigerant or cooling water. As aresult, high-purity butadiene may be obtained while reducing the amountof active ingredients discharged to the outside, thereby improvingeconomic efficiency of processes.

Hereinafter, the present invention will be described in more detail withreference to the following preferred examples. However, these examplesare provided for illustrative purposes only and should not be construedas limiting the scope and spirit of the present invention. In addition,it will be apparent to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present invention, and such changes and modifications are alsowithin the scope of the appended claims.

EXAMPLE Example 1

To obtain oxidative dehydrogenation reaction products containingbutadiene, oxidative dehydrogenation of reaction raw materials includingbutene, steam, and butane in molar ratios of butene:oxygen=1:0.9,butene:steam=1:5, and butene:butane=1:2 was performed under the presenceof a ferrite catalyst in the device for preparing butadiene according toFIG. 2. In this case, butane was used as a diluent gas, and raffinate-3having compositions shown in Table 1 below was used as a butene source.Then, water was removed from the obtained oxidative dehydrogenationreaction products. The water-removed oxidative dehydrogenation reactionproducts were introduced into a condensation separation part, andpressurized at a compression discharge temperature of 80° C. using atwo-stage compressor, and hydrocarbons were condensed at 40° C. usingcooling water. Thereafter, to minimize loss of effective hydrocarbonspresent in the vapor phase of the condensation separation part to theoutside, crude hydrocarbons were obtained by absorbing all hydrocarbonsusing toluene in the absorption separation part. Then, the crudehydrocarbons were fed into the purification part, and purification andrecovery processes were performed using DMF as a solvent to obtainbutadiene having a final purity of 99.7% by weight.

In this case, the compositions of the discharge streams (B2, B3, B4, B5,B6, B7, B8, final product) of each of the cooling separation part, thecondensation separation part, the absorption separation part, and thepurification part were calculated using a process stimulator(AspenPlus), and the results are shown in Table 2 below.

In addition, the amounts of the solvent and energy used in theabsorption separation part and the purification part are shown in Table4 and Table 5, respectively. Energy units per mass of butadienecalculated accordance with heat exchange in the butadiene preparationprocess are shown in Table 6, and the recovery rate and purity of theobtained butadiene are shown in Table 7.

Comparative Example 1

Except that the device for preparing butadiene according to FIG. 1 wasused, and nitrogen was used as a diluent gas, experiments were performedin the same manner as in Example 1. As a result, butadiene having afinal purity of 99.7% by weight was obtained.

In this case, the compositions of the discharge streams (B2, B3, B4, B5,B6, final product) of each of the cooling separation part, thecondensation separation part, the absorption separation part, and thepurification part were calculated using a process stimulator(AspenPlus), and the results are shown in Table 3 below.

In addition, the amounts of the solvent and energy used in theabsorption separation part and the purification part are shown in Table4 and Table 5, respectively. Energy units per mass of butadienecalculated accordance with heat exchange in the butadiene preparationprocess are shown in Table 6, and the recovery rate and purity of theobtained butadiene are shown in Table 7.

TABLE 1 Composition % mol % by weight 1-butene 0.00 0.00 Trans-2-butene43.20 42.77 Cis-2-butene 28.80 28.51 n-butane 28.00 28.72

TABLE 2 Condensation separation part 230 and absorption separation part250 Purification part 240 Pressure 0.3 10.9 7.0 4.5 3.7 4.5 3.7(kg/cm²g) Temperature 35.0 40.0 78.5 51.2 47.4 55.6 42.1 (° C.) Massflow rate (kg/hr) Final B2 B3 B5 B4 + B6 B7 B8 product Oxygen 1,919.41,836.5 1,919.3 — — — — Nitrogen — — — — — — — COx 4,028.0 3,181.24,026.1 — — — — Water 4,040.3 29.1 43.2 — — — 0.1 Light gases* 3.3 2.03.3 — — — — Carbonyl and 59.8 3.8 18.3 40.6 — — — aldehyde 1-butene209.4 15.8 8.0 201.4 201.4 — 0.0 1,3-butadiene 18,741.6 1,480.8 846.917,840.5 30.3 50.0 17,639.5 n-butane 49,250.0 3,350.0 1,217.4 48,032.548,032.5 — — Acetylenes 22.5 2.1 2.1 20.4 — 0.0 0.0 Trans-2-butane1,786.3 117.8 28.7 1,757.5 1,747.0 3.6 6.9 Cis-2-butane 609.4 37.8 6.3603.2 293.7 261.3 47.5 High-boiling 137.1 0.9 115.4 75.5 — — — pointmaterials ** Toluene — — 310.9 0.0 — — — DMF — — — — 17.8 — — Sum80,807.1 10,057.7 8,549.9 68,571.7 50,322.4 314.9 17,694.0 *Light gasspecies: gases having lower boiling points than that of the C4 fractionexcluding COx and O₂. ** High-boiling point materials: aromatichydrocarbons, such as benzene, styrene, and phenol, butadiene dimers,acetophenone, benzophenone, or anthraquinone

TABLE 3 Absorption separation part 130 Purification part 140 Pressure3.6 3.0 4.5 3.7 4.5 3.7 (kg/cm²g) Temperature 40.0 46.3 48.1 47.3 54.542.1 (° C.) Mass flow rate (kg/hr) Final B2 B3 B4 B5 B6 product Oxygen2,720.3 2,720.3 — — — — Nitrogen 19,018.1 19,018.1 — — — — COx 4,025.54,025.5 0.0 0.0 — — Water 447.6 212.9 234.8 — — 0.2 Light gases* 3.3 3.3— — — — Carbonyl and 59.2 29.7 26.5 — — — aldehyde 1-butene 209.4 32.2177.2 177.2 — — 1,3-butadiene 18,736.2 1,376.3 17,359.6 30.0 50.017,140.6 n-butane 9,573.7 1,768.8 7,804.8 7,804.8 — — Acetylenes 22.50.1 22.4 — — — Trans-2-butane 1,785.8 107.7 1,678.0 1,667.0 3.1 8.0Cis-2-butane 609.3 17.1 592.1 410.8 137.7 43.5 High-boiling 136.3 128.7— — — — point materials ** Toluene — 1,900.3 — — — — DMF — — — 0.6 — —Sum 57,347.1 31,340.8 27,895.4 10,090.3 190.8 17,192.1

TABLE 4 Amount of solvent used (ton/hr) Comparative ClassificationExample 1 Example 1 Absorption 18.4 237.6 separation part (toluene)Purification part 290.0 160.0 (DMF)

TABLE 5 Total amount of energy used (Gcak/hr) Comparative ClassificationExample 1 Example 1 Absorption 9.8 24.3 separation part Purificationpart 44.7 35.4 Sum 54.4 59.8

TABLE 6 Comparative Example 1 Example 1 Energy unit per 266 297 unit BD($/ton)

TABLE 7 Comparative Classification Example 1 Example 1 Recovery rate of94.1% by 91.5% by butadiene weight weight Purity of butadiene 99.7% by99.7% by weight weight

As shown in Table 4, in the case of Example 1 according to the presentinvention, butane is used as a diluent gas, and some hydrocarbons arerecovered through compression and cooling in the condensation separationpart. Accordingly, when hydrocarbons are recovered in the absorptionseparation part, the amount of the solvent used is significantly reducedin comparison with Comparative Example 1. On the other hand, in the caseof the purification part, the amount of the solvent used in Example 1 isincreased compared to that of Comparative Example 1 due to butane usedas a diluent gas. However, as shown in Table 5, in the case of Example1, the total amount of energy used in the absorption separation part andthe purification part is greatly reduced as compared with ComparativeExample 1.

In addition, as shown in Table 6, the energy unit per unit mass ofbutadiene in the butadiene preparation process is 266$/ton in Example 1and 297$/ton in Comparative Example 1. That is, as compared withComparative Example 1, energy consumption in Example 1 is significantlyreduced.

In addition, as shown in Table 7, butadiene recovery rate in Example 1is higher than that in Comparative Example 1, on the basis of whenbutadiene has the same purity. That is, in the case of Example 1,productivity and economic efficiency may be improved.

DESCRIPTION OF SYMBOLS

-   -   110, 210, 310, 410, 510, 610: OXIDATIVE DEHYDROGENATION REACTION        PART    -   130, 250, 350, 450, 550, 650: ABSORPTION SEPARATION PART    -   120, 220, 320, 420, 520, 620: COOLING SEPARATION PART    -   230, 330, 430, 530, 630: CONDENSATION SEPARATION PART    -   140, 240, 340, 440, 540, 640: PURIFICATION PART    -   360, 460, 560, 660: DEGASIFICATION PART    -   370, 470, 570, 670: SOLVENT RECOVERY PART    -   480, 680: HIGH-BOILING POINT MATERIAL REMOVAL PART    -   531, 631: COMPRESSOR    -   532, 632: HEAT EXCHANGER

The invention claimed is:
 1. A device for preparing butadiene, comprising: an oxidative dehydrogenation reaction part, in which oxidative dehydrogenation of reaction raw materials containing butene, oxygen (O₂), steam, and butane as a diluent gas is performed to obtain oxidative dehydrogenation reaction products containing butadiene, water, n-butane, butene, CO_(x), and O₂; a cooling separation part responsible for removing the water from the oxidative dehydrogenation reaction products; a condensation separation part responsible for condensing hydrocarbons from the oxidative dehydrogenation reaction products, from which the water is removed; an absorption separation part responsible for recovering all hydrocarbons from the oxidative dehydrogenation reaction products containing hydrocarbons not condensed in the condensation separation part; and a purification part responsible for separating the butadiene from crude hydrocarbons comprising the n-butane, the butene, and the butadiene condensed in the condensation separation part, and separating the butadiene from crude hydrocarbons comprising the n-butane, the butene, and the butadiene, excluding the CO_(x), and the O₂, which are recovered in the absorption separation part, wherein the n-butane remaining after the butadiene is separated in the purification part is fed again into the oxidative dehydrogenation reaction part.
 2. The device according to claim 1, further comprising a discharge stream responsible for feeding the crude hydrocarbons comprising the n-butane, the butene, and the butadiene, which are recovered in the absorption separation part, into the purification part.
 3. The device according to claim 1, further comprising: a solvent recovery part responsible for recovering a solvent from a discharge stream containing hydrocarbons comprising the n-butane, the butene, and the butadiene, which are recovered in the absorption separation part; and a discharge stream responsible for refeeding the solvent recovered in the solvent recovery part into the absorption separation part.
 4. The device according to claim 3, further comprising a degasification part responsible for separating the CO_(x) and the O₂ from hydrocarbons comprising the n-butane, the butene, and the butadiene, which are recovered in the solvent recovery part.
 5. The device according to claim 4, further comprising a discharge stream responsible for feeding the CO_(x) and the O₂ separated in the degasification part into the absorption separation part.
 6. The device according to claim 4, further comprising a discharge stream responsible for feeding the CO_(x) and the O₂ separated in the degasification part into the condensation system.
 7. The device according to claim 5, further comprising: a high-boiling point material removal part responsible for removing high-boiling point materials from crude hydrocarbons comprising the n-butane, the butene, the butadiene, and high-boiling point materials, excluding the CO_(x) and the O₂, which are separated in the degasification part; and a discharge stream responsible for feeding crude hydrocarbons comprising the n-butane, the butene, and the butadiene, which are separated in the high-boiling point material removal part, into the purification part.
 8. The device according to claim 6, further comprising: a high-boiling point material removal part responsible for removing high-boiling point materials from crude hydrocarbons comprising the n-butane, the butene, the butadiene, and high-boiling point materials, excluding the CO_(x) and the O₂, which are separated in the degasification part; and a discharge stream responsible for feeding crude hydrocarbons comprising the n-butane, the butene, and the butadiene, which are separated in the high-boiling point material removal part, into the purification part. 